The invention relates to a sintered transformer core of MnZn-ferrite material. The invention further relates to a transformer comprising such a core. By means of a transformer the voltage and/or current of a current source can be transformed into a desired different voltage and/or current.
A transformer core of the type mentioned in the opening paragraph is known per se. Said core consists of sintered MnZn-ferrite which is described under code number 3C85 in Philips' Data Handbook C4, 1986, page 13. The sintered ferrite material of the known transformer core has an average grain size of 9 .mu.m and exhibits an initial permeability (.mu..sub.i) of 2000. The initial permeability is measured under standard conditions, i.e. at room temperature and 4 kHz. The known transformer core exhibits optimum properties when it is operated at frequencies of approximately 100 kHz and an induction of 100 mT. Under said conditions, in particular, the so-called overall losses (P) are relatively low, i.e. below 250 mW/cm.sup.3. Said low losses can be ascribed to the high initial permeability of the ferrite material.
The known transformer core exhibits disadvantages. It has been found that the overall losses increase considerably when the core is used in the MHz-frequency range, more particularly in the range of 2 MHz and higher. The overall losses of the known core are 410 mW/cm.sup.3 at 3 MHz (induction 10 mT) and even 800 nW/cm.sup.3 at 10 mHz (induction 5 mT). These relatively large losses cause a strong heating up of the transformer core and transformer housing. Consequently, the known core is less suitable for use in transformers which are operated in the frequency range of 2 MHz and higher.